Thursday, April 18, 2013

Adventures with Libhybris and Andriod

As promised in my tweet at the weekend I'm going to give some more details on the steps required to get Mer based gfxs apps running on top of Android graphics drivers on the Allwinner A10 based cubieboard. This work was inspired by this blogwhich sets out the dilemma we face when trying to port regular GNU Linux to fantastic mobile devices.So, what do you need, well specifically a cubieboard but any Andriod device running a recent version which allows you to boot your own kernel is a potential target for Mer and Libhybris. On the software side you need an Android development environment, access to the andriod source repo for your device, patch for bionic (android's version of libc) and the libhybris library. The reason we need all this android stuff is so that we can rebuild the android bionic library with a couple of tweaks which will allow bionic and libc libraries coexist in our final build.So first follow these instructions to setup your Android build environment, I welcome any questions on this blog post except this section, please beware this is the most frustrating things I've done in ages and would not like to re-live it. There are plenty of sources of help on the web, if you're lucky the stars will align and you will have no problems.http://source.android.com/source/initializing.html and the installing repo section from http://source.android.com/source/downloading.html

Now you need access to the Andriod source repo for your device, I will be giving cubieboard specific instructions from now but all Andriod devices have a similar repo structure. There are a couple of pages with Andriod for cubieboard but this is the one I used, https://github.com/cubieboard/manifests. It does give some instructions on setting up a dev environment which I've not tried but you may be more successful than my attempts.So following that page

You will have time for more than lunch!So the build should complete with some messages about creating a system.img file. Congratulations you've just built your first Android ROM.Next we need to patch the bionic library so descend into the bionic directory and apply this patch and rebuild

$make -j4

Now we have to tar up the android system directory so we can install it on the device. This will have the patched bionic library plus all the andriod libs (EGL, GLESv2, RIL etc) which we will now be able via libhybris to access from regular glibc apps. This will be at out/target/product/cubieboard/system.Ok so next step is to get a minimal Mer image for your device, this is another blog post in itself so I've created a basic image here. Download this and write to an sdcard and boot in the cubieboard. It should boot to xterm on hdmi.Ok, so we don't want X to start anymore so from VT2 login root/mer and remove uxlaunch before rebooting.

$zypper -e uxlaunch

On next boot X will not start so login again from VT2.Now we can install libhybris.

Next copy the android system dir we made a copy of earlier to /systemNow we can test libhybris is installed correctly

$test_egl

This should give some messages but if all is well it should not crash and print 'stop'

$test_glesv2

This should show a white diamond shape filled with an animated Catherine wheel. Congrats you are now running an EGL/GLES glibc application linking to the Android EGL/GLES bionic drivers.Next we can now run a couple of more interesting demos

So if you've reached this far thanks for reading and if you have used a different Android device please let us know on #mer or #libhybris.As usual in the open source world we are always building "on the shoulders of giants" so a few thanks to the giants.Stskeeps for his awsome contributions not just with libhybris but all things Mer and also his patience with me. Thanks to the wider Mer and libhybris teams.

On the cubieboard front thanks to the linux-sunxi team for their work on the bootloader and kernel and to mdfe for his excellent Mer adaptation packaging and awesome Jenkins buld system.TTFNvgrade - catch me in #mer on freenode IRC

Hi, thanks for your sharing and I'd like to try it out on my Android device.I have got the android source and built an image running on my device. somehow I cannot access the the bionic patch in your post, and I found this one (http://wklej.org/id/1308620/), can you help confirm whether it's the same patch as the one you used?